The objective is to learn how cilia move mucus. High speed cine and flash photomicrography will be carried out on isolated pieces of mucosa from the trachea of rabbits and various rodents, the palate of several frogs, and the gills and palps of several bivalve molluscs, using Nomarski interference-contrast optics. Ciliary beating rate and form, movement of tracer particles in the serous fluid, and transport of surface mucus will be measured from tracings of projected film. Viscoelastic properties of mucus will be determined from measurements of resistance to flow and elastic deformation in a micro-viscosimeter. The distribution of mucus, its thickness, and its relationship to the cilia will be ascertained by scanning and transmission electron microscopy of tissue fixed at various stages of the experimental procedure. Experiments employing changes in temperature and humidity, pharmacological agents, and the addition of artificial media to the mucosal surface will be carried out in an attempt to selectively alter ciliary beating, serous fluid or mucus. The effects of these changes on other components of the system will be observed and an analysis made of the interaction of cilia, serous fluid and mucus in the overall phenomenon of mucociliary transport.